Question

(iv = independent variable, dv = dependent variable, cv = controlled variable)
derek had 3 tanks of tadpoles. one tank was under a red light, one tank was under a green light and the third tank was under a white/natural light. derek counted the number of days until the tadpoles had fully developed legs.
iv\tdv\tcv
the type of food given to the tadpoles

the type of tadpoles

the number of days until the tadpoles had legs

the color of light

the age of the tadpoles

Explanation:

The independent variable (iv) is what the experimenter changes. Here, the color of light is being changed (red, green, white - natural). The dependent variable (dv) is what is being measured, which is the number of days until the tadpoles have fully developed legs. Controlled variables (cv) are kept the same. The type of food and type of tadpoles and age of tadpoles are likely kept the same to ensure only the light - color variable affects the result.

Answer:

The type of food given to the tadpoles: cv
The type of tadpoles: cv
The number of days until the tadpoles had legs: dv
The color of light: iv
The age of the tadpoles: cv